ESBCalc is a Free Scientific Calculator software that can be portably run from a USB drive in Windows. It supports Infix Notation, Brackets, Scientific Functions (Trigonometric, Hyperbolic, Logarithmic "Base 10, Base 2 & Natural"), Memory, Paper Trail, Result History List and more.
Convert is a unit conversion tool that can convert some of the most common units of measurement including distance, density, energy, temperature, time, speed, volume, mass, power, pressure and much more. Convert is free, tiny and very easy to use which makes it a perfect candidate to add to your USB flash drive.
On Screen Ruler is a free portable tape measure tool made by John Kummailil. It was initially created simply to teach kids about computers and software development.
Calculor is a free Calculator that can be stored and run from a USB flash drive. It is a simple to use and straightforward calculator that calculates live answers as you type.